He ran full-tilt away from another potentially titanic confrontation with Gov. Cuomo last week — this one about housing subsidies — after absorbing an astonishing public thrashing from the governor in February over gouge-the-rich taxation and charter schools, among other things.

Public humiliation can be a terrific teaching tool, and Cuomo has neither spared the rod nor spoiled the mayor, beginning on Day One. (But always wearing a smile, of course).

So when City Hall last week suggested strongly that Cuomo find cash for an expansion of welfare housing subsidies, the governor bristled and de Blasio blanched. Murmuring about how well he got along with the governor at HUD back in the day, the mayor quickly chalked it all up to a “misunderstanding” and moved on.

Clearly de Blasio had learned an important lesson: If you’re going to tug on Superman’s cape, bring kryptonite — which, too bad for the mayor, is in short supply in Metropolis these days.

Which is to say that the towering tsunami of a mandate that de Blasio insists carried him into office was in fact something much less — a tidal surge, maybe.

None of this was obvious to the mayor, of course. For if de Blasio’s 73% of the November vote wasn’t a mandate, then what in the world was it?

Here’s the answer: There were, in fact, two elections last year, and de Blasio underperformed in both:

The first was the pratfall-filled Democratic primary (lookin’ at you, Carlos Danger!) de Blasio won it by default, having made fewer mistakes than his opponents — much like the speed-skater who grabs Olympic gold after all the other skaters fall down in the final turn.

Then there was the general election, which de Blasio won handily — but with the backing of a minuscule 18% of New York’s registered voters. The remaining 83% either voted for somebody else — or, overwhelmingly, simply didn’t vote at all.

De Blasio did win, of course, and he gets to govern.

And while his numbers represent no compelling instruction from the voters, they do reflect a constituency: The same hard-left-leaning core of ideologues, activists and special-interest operators that also captured the City Council and the public advocate’s office on Election Day.

De Blasio has hewed pretty close to that hard-left line — but those beliefs simply do not reflect the city at large. That much becomes clear from the polls, which report that voters are giving the new administration — and de Blasio in particular — the fish-eye.

The Q-poll pegged de Blasio’s own job approval at an embarrassing 45% — a sharp drop from 53% in January. Disapproval, on the other hand, leapt from 13% in January to 34% in the current account.

Apart from the polls, virtually every major de Blasio campaign platform plank — a millionaires’ tax; a scaling back of charter schools; a rescue for Brooklyn’s Long Island College Hospital and the banishment of carriage horses from Central Park — has either been defeated outright or is on long-term hold.

And his one seeming big win — a richly funded pre-K program — is proceeding only at Cuomo’s sufferance and without the ritual bleeding of the wealthy that de Blasio originally demanded.

Reversals such as de Blasio has suffered simply don’t happen to new mayors with powerful mandates — and this new mayor seems finally to be coming to terms with the fundamental shallowness of his base.

Certainly he moved toward the mainstream on charter schools last week, even if it does remain to be seen if he really means it.

Support for chartered public schools is real and growing, and this is reflected both in the polls themselves, and in increased backing from acutely poll-conscious politicians like Cuomo.

The teachers unions despise charters, of course, and de Blasio has been overtly hostile to them throughout his career — never more vehemently than during last year’s campaign.

That seemingly began to change this month — right after Quinnipiac reported that 79% of city voters essentially approve of charters, at least in principle.

Last Sunday de Blasio travelled to Riverside Church to offer an armistice of sorts with the charter movement, even promising later in the week to try to get along better with charter-school nemesis Eva Moskowitz, who runs a string of stunningly successful charters.

De Blasio’s willingness to respond to public opinion in so dramatic a fashion suggests that — when it comes to mandates — he finally understands that he ain’t got one.

If so, that could be Step One on the long road to a successful mayoralty — the outcome all New Yorkers of good will so ardently desire.